Default 3g/Calls Not working s3

Hello, i'm from brazil and i have a little problem from my sgs3, with my signal. I only can make emergency calls, and appears on the screen "no service" . I'm using the 4.4.2 custom rom (Blekota) , but the most unusual is, some roms 4.4.2 i have signal, example ( Ressurection Remix ) . How can i fix it ?